1. Field of the Invention
The present invention pertains to a resilient rail fastener of a novel configuration formed from springsteel for securing rails to cross ties utilizing two spikes or screws per rail clip that provides an exceptionally effective clamping force while dampening and distributing acceleration and vibrational forces resulting from load conditions during train passage. More particularly, the invention relates to the application of a springsteel rail clip of a trapezoidal configuration having a novel sine shaped curve along the rail biasing edge which is flattened when fully tightened against the foot of the rail. The novel configuration of the clip along with its springsteel construction functions to dampen accelerational forces and vibrational frequencies of the rail in the range of from 800 to 1000 Hz that have heretofore caused deterioration and a reduction of the useful life of rail ties. The utilization of the two spikes or screws per clip allows each bolt to provide about 1,500 lbs. of pressure to secure the rail to the tie while allowing the rail clip to dissipate shock and imact vibrations that would otherwise impair the integrity of the rail spike.
2. Description of the Prior Art
The prior art includes a variety of devices which illustrate a myriad of rail clips and fastening systems for fastening rails to a rail tie. The effectiveness of the combination of rail clip and spike or screw depends not only upon the traffic conditions but also the type of railroad tie, the number of spikes or screws per rail clip and the configuration of the rail clip which functions to absorb impact and transfer of load to the substrate rail tie. In addition to the vertical forces and vibrations acting upon the rail tie and clip, there are high lateral forces which in combination with the vertical forces produce stresses and strains on the rail fastening system which primarily includes the rail tie, the rail clip and the spikes or screws. Heavy axle loads, unit trains of long lengths and load uniformity and higher operating speeds subject the rails to high lateral forces along with acceleration forces which result in rotation of the rails and rail spreading. The accelerational and vibrational forces promote fatigue in the wood or concrete tie which together with the effect of the environment and aging, significantly account for high maintenance and derailments in the railroad industry.
The prior art pertaining to rail fastening systems in the United States focuses primarily uppon wooden ties and a steel tie plate which utilizes two spikes on opposite sides of the rail base for each tie plate. The steel tie plates used in the United States include four spike holes for securing the rail to the tie plate and tie, but which in practice employ only two spikes. The combination of vibrations of high frequency and dynamic impact upon the conventional rail spike results in deterioration of wooden ties by cracking and splintering the wood surrounding the rail spike resulting in the rail spike loosing contact with the rail base. As is all too well known to those skilled in the art, spikes have to be periodically tightened by work crews and sometimes the rail tie must also be replaced where the tie has splintered or otherwise deteriorated in use. This deterioration of the securement between the rail and rail tie is generally attributable to the high frequency vibrations and dynamic impact from acceleration and deacceleration forces which cause the heads of the spike to project a considerable distance above the railbase and result in the rail losing its stability followed by rail spread which in many cases leads to derailments.
Representative of the prior art utilizing wood fastening systems is U.S. Pat. No. 2,218,156 which provides a resilient clip for dampening vertical forces which is apparently used in combination with wooden ties. This patent illustrates a two bolt per clip arrangement (FIG. 4) but does not longitudinally dampen vibrations and forces and can be overtightened which would exceed the elastic limit of the springsteel. The rail fastening clip as illustrated in U.S. Pat. No. 1,798,357 is of a general trapezoidal configuration, but which in function and operation is different from the rail clip of the present invention. In U.S. Pat. No. 1,798,357, the resilient rail clip is biased against the rail with the short end of the trapezoidal rail clip against the rail base with the long edge of the trapezoidal configured rail clip biased against the edge of the rail. This rail clip is then rendered compatible with the traditional two spike tie plate utilized in the United States by the utilization of a clip in combination with the plate spring. The rail fastening system of U.S. Pat. No. 1,798,357 is considerably different from the present invention, since it not only employs a U-shaped (FIG. 13) rather than sine shaped curve, but also utilizes spikes at a different point and combines a number of elements that do not correspond to the clip of the present invention.
Many of the prior art rail clips utilized in European rail systems employ a concrete rail tie and provide a resilient clip to absorb much of the forces that the wooden ties absorb in the United States rail systems. In the European systems a single screwpike is utilized along with a resilient rail clip and elastomer rail pad to absorb vibrations between the concrete and metal screws which would otherwise cause cracking of the concrete. Such clips have generally not been utilized in United States rail systems because of the incompatibility of the single rail screw to the United States two spike system. In addition, the rail clip having single screwpikes, such as illustrated in U.S. Pat. No. 4,054,247, is not amenable to a side by side disposition or a double bolt application where the dynamic forces upon the rail dictate additional securement.
The configuration of the prior art rail clip, as depicted in U.S. Pat. No. 3,796,369, is similar in some respects to the present rail clip. However, unlike the present invention, U.S. Pat. No. 3,796,369 utilizes a single rail screw for concrete rail ties and does not use the sinusoidal curved edge to bias the rail base or foot. Furthermore, in use the sinusoidal curved portion in its stressed condition (FIG. 3) is not completely flattened. The present invention while employing a sinusoidal curve stresses the sinusoidal curve to completely flatten the curve along the length of the rail base.
The prior art rail clips have generally been designed to dampen only one of the two forces encountered in the passage of train loads over the rail tie. One such prior art system which has been traditionally employed in the United States utilizes a single spike on each side of the rail base and secures the rail to the tie with a force of only about 2,500 lbs. The European prior art systems which have generally employed a resilient clip and a single screwpike per clip to fasten the rail to the tie provides a force of about 4,500 lbs. In addition, many of these prior art systems utilize clips which may be over-tightened resulting in damage and decreased efficiency of the fastening system. The present invention, however, cannot result in damage to the rail clip by overtightening and is compatible with either the United States or European rail systems by accomodating either two screwpikes or the two traditional spikes per clip to fasten the rail to the rail tie utilizing a force of 1,500 lbs. per spike or 3,000 lbs. per rail clip resulting in a total force of 6,000 lbs. or about 1,500 lbs. force greater than the prior art systems.
The configuration of the novel rail clip of the present invention even more importantly allows both lateral and vertical forces to be dampened along the entire length of the rail clip and is particularly effective in absorbing and dampening vibration frequencies in the range of 800 to 1000 Hz. which is the natural frequency of the rail and which has been particularly damaging to rail fastening systems.